Transmission Computer: Controllers - In Control

With stand-alone control of electronically controlled overdrive automatics, it's easier to dial in accurate upshifts, and you can just stab the throttle, steer it, and the trans will do the rest. The performance world is changing. While power remains almighty, the new world is all about how to get that power to the tires. The best way to control an automatic transmission is to use one of the new, electronically controlled overdrive gearboxes (Transmission Computer). But swapping one of these newer transmission computer e-trannies into an older muscle car requires some type of aftermarket, stand-alone transmission controller. Names like EZ TCU and Simple Shift made us wonder if these controllers could live up to their hype. The only way to know for sure was to put them to the test.

We gathered five different transmission computer controllers and subjected them to a real-world flogging on a big-block street car to see if each could do the job. All the controllers perform the same basic functions, allowing you to custom-tailor shift points both at part- and wide-open throttle, as well as shift firmness at various throttle openings. How specifically each box accomplishes these tasks and how easy it is to effect changes are the key questions. Perhaps the most important differentiation for the average enthusiast is whether the box requires a laptop computer or relies on a hand-held device with analog controls.

Transmission Computer: Our Test Mule

The best way to test these controllers was to bolt them all in the same car and evaluate their performance. Car Craft family member Ed Taylor recently purchased a '70 Nova that had been languishing in front of Ken Duttweiler's shop for several years. We power-washed the grease left behind by the previous turbo Buick V6 and bolted in a Holley, carbureted, 496ci big-block Chevy. You might recall the "Rat" as the dyno mule we whipped mercilessly for a big-block oval-port-head test in our Mar. '08 issue ("Big-Block Cylinder Head Test," pg.30). Behind our 590hp, 620-lb-ft rodent, we bolted a used 4L80E that Ed Taylor scored from Craigslist. We stuffed the 4L80E into the car using a TCI flexplate and a 10-inch lockup Street Fighter torque converter along with a very nice custom aluminum crossmember from American Powertrain and a Dynatech aluminum driveshaft, and the big pieces were in place. Of course, it took more than just a motor and trans to turn this orphan into a road warrior

Other goodies we wanted for the buildup included a new pair of bucket seats from Scat to replace the aged originals and a new set of Toyo Proxes R888 sticky 17-inch tires obtained through our pals at TreadSource and mounted on lightweight RT-S Weld wheels. With the big-block squeezed in, there was no room for a mechanical fan, so we opted for a pair of electric fans from Maradyne mounted to a killer Afco aluminum radiator. That combination worked to prevent the engine temp from exceeding 195 degrees F. We also added a set of Wilwood front disc brakes because the Rat promised enough power to demand equal stopping performance. For the intake, we needed a 950hp Holley to feed the Rat, and for the exhaust side a pair of Hedman 2-inch headers snaked around the stock manual steering box. We completed the exhaust with a great-sounding, 2.5-inch cross-pipe system from MagnaFlow installed by our pal Kevin McMillan. After two months of busted- knuckle work, the car was up and running, and we were ready for street testing.

No Magic Box

One of the first things we discovered when we began testing controllers is that we had unintentionally combined a very high-torque engine with a loose converter and a used 4L80E transmission. We began questioning the first couple of controllers when even with maximum setting on the trans line pressure, we couldn't get the rear tires to bark on the gear changes. After we talked with the controller manufacturers, one point became very clear: The controller is not a magic fix for a weak transmission. HGM Automotive, the builders of the CompuShift II, told us it designs its box to be used with a new transmission and assumes the trans has been modified for performance use. So when we were not able to hit the rear tires as hard as we felt appropriate for a performance application, it was obvious that while our transmission was in decent shape, it was not capable of what you might call harsh shifts without some help in terms of a mechanical shift improver kit or even a rebuild with new clutches. If you are contemplating the use of a previously owned transmission, remember that even the best controller cannot compensate for a weak or damaged transmission. This is less of a disclaimer as it is an acknowledgement of the physical capabilities of the transmission.

While all the controllers offered the option of using a paddle shifter or up and down buttons to shift, we opted to merely place the TCI floor shifter in Drive and modify the controllers to get the transmission to shift at the correct rpm for each gear change. We thought most car crafters would prefer this method. While we didn't test the paddle-shifter options, there's no doubt that each of the controllers would be fully capable of making those electronic gear changes.

Tuning Tricks

There are several ways to tune these electronic transmissions. Though the process may seem confusing at first, once you know what each step represents, understanding the effects of these inputs will make you a better tuner. For example, the maximum engine rpm input is not a rev limiter. It is actually the maximum shift rpm default at which the transmission will always upshift. But maximum rpm is the point at which the transmission begins the shift process. For example, PCS told us that depending on the condition of your transmission, it could take anywhere from 400 to 800 rpm to complete the shift. So if you indicate a 5,500 maximum engine rpm in the controller, the engine could reach as high as 6,300 or more before the shift is completed. If you don't want the engine to rev past 5,500, you need to experiment with a lower maximum engine rpm limit.

We should also discuss line pressure. The CompuShift II, for example, offers a standard called PRB or pressure boost. Most of the other controllers indicate a similar parameter expressed as a percentage of available hydraulic pressure. The CompuShift II will command pressures between zero and 100 percent of available pressure from the transmission. Absolute pressure is what the trans is capable of producing and is measured from a pressure gauge connected to a tap on the transmission case.

If your transmission is equipped with a lockup torque converter, there are several tuning areas available for torque converter clutch (TCC) lockup. Maximum TCC lockup is usually expressed as the percentage of TPS or throttle opening. Most converters will not lock up past 50 percent TPS to prevent damage to the lockup clutch. There are separate options for minimum TCC lockup, as well. For larger engines like ours, it's best to set the lockup minimum at zero percent to prevent the clutch from oscillating at lower throttle openings. If the percentage is set too high, a very light throttle opening may not achieve TCC lockup at highway cruise speeds. This will also retain lockup under deceleration. Most controllers also feature a brake-light switch that unlocks the converter anytime the brakes are applied.

Most of the controllers also offer a simple way to toggle between two different calibrations. For example, you could have calibration A set up with a performance orientation with aggressive upshift speeds and higher line pressures, while calibration B could be used for towing or light-duty daily driving applications. The controllers with this feature include a single wire that is grounded with a simple toggle switch to switch calibrations.

The Painless Torc and others also require saving the changes you've made to the ECM to write the new commands into the controller. Otherwise, when switched, 12 volts is turned off, the changes will not be saved, so it's best to get into the habit of saving all changes to ensure they are not lost.

HGM Compushift II ($1,136.08)

HGM Electronics created the original CompuShift electronic controller soon after the original GM 4L60E began appearing in Chevrolet cars in the early '90s. The new and improved CompuShift II controller uses a separate handheld module from the transmission control unit (TCU). The remote can be permanently mounted within reach of the driver or retained as a portable unit. The CompuShift II is advertised as "No Laptop Required," and that's the way we used it, but you can connect a PC to the box if desired. The CompuShift II can also be used in conjunction with a paddle shifter or pushbuttons mounted on the steering wheel. The harness connections are clearly marked, which makes installation easy. In lieu of a laptop, it uses a separate display module with a good-size screen and seven buttons used to navigate the program to change shift points, shift firmness, and other variables. This made the initial work on the controller very simple.

The CompuShift II display can also indicate vehicle speed, engine rpm, trans temperature, and gear position in large digits that are very easy to read. One aspect we liked and saw in only one other controller was an input for vehicle weight. This input takes into account the mass of the vehicle for more accurate shift parameters.

Among all the nonlaptop controllers we tested, the CompuShift II was the easiest to navigate, and its program was as close to optimal as any of the others we tested. The only thing preventing this controller from making the top of our list is the absence of a data-logging feature. But that takes nothing away from its overall performance and excellent adjustability. The feature that most impressed us (under Advanced Setup) was Shift Tables, in which each screen offered shift pressure tuning down to 1 percent changes in TPS. That's very cool. Most people probably wouldn't bother tuning that precisely, but we thought it was a great feature. The only other systems that offered that kind of precise control were the laptop-driven programs. It offers outstanding finite control from a handheld unit.

GMPP Supermatic ($1,139.33)

The GM Performance Parts (GMPP) controller is the only controller we tested that requires a laptop not only to configure the software but also to make changes to the shift values. This requires some basic computer skills, but the software is designed to be easily modified. Setup data is critical to optimized operation, so details such as tire diameter, rear gear ratio, engine cylinder count, and TPS open and closed voltages are essential inputs. The software also offers two shift schedules that can be easily swapped merely by grounding the Shift Schedule Selector wire with a toggle switch. We should also note that the box came with a basic program already in place (as do all the controllers apart from the PCS Simple Shift), so once you have accurate input data and have configured the TPS range, no further work is necessary to make the trans shift acceptably. The initial configuration was nearly ideal and only required a couple of minor part-throttle upshift changes.

Apart from the advantages of specific changes to shift or pressure curves, perhaps the most important benefit of the Supermatic software is its data-logging feature. Rather than having to purchase separate software, the data-log option offers the opportunity to review a dragstrip run, for example. There are so many channels of data available, we won't even try to list them all. Suffice it to say that if you want trans info, it's in there.

We didn't have the time to really investigate the data-logging feature, but we logged five minutes worth of data just to see what came up. Consider data-logging a dragstrip pass and then carefully evaluating exact shift points, possible tire spin (which can be seen as spikes in mph), and other variables like shift duration and fluid temperature. This is all possible because of the sensors present in these newer transmissions. Sensors and a separate data logger would cost hundreds of dollars, but with the GMPP Supermatic controller, the data logging is a no-cost benefit.

While the controller may appear complex, we spent very little time tuning and navigating this particular unit. Only the EZ-TCU was easier. We have to admit we've had plenty of laptop tuning experience dealing with EFI systems, so we're not rookies. But consider, too, that if you have a buddy with a laptop who has some experience tuning with a computer, tweaking this system wouldn't be difficult. And once you have a shift program you like, there will be very few reasons to ever change it. Tuning complexity shouldn't be a reason to pass on this system.

Painless Torc ($859.95)

The Painless Torc transmission controller wins the packaging award as the smallest control box of all the units we tested. Both the handheld device and the controller are in a 23?4 by 41?4-inch interface that can either be permanently mounted in the dash or console or hidden in the glovebox. The system comes with a very nice color installation/instruction manual with clear wiring diagrams for harness connections. The controller allows you to scroll through several parameters to set part-throttle and WOT upshifts as well as shift firmness and TCC engagement. If you choose to load the Shiftware software into a laptop, the unit offers a USB connection instead of the older serial port that requires an adapter and software. Sometimes these adapters can be troublesome. The laptop software allows you to customize the shift points with more finite control than with the handheld interface. We loaded the software, but we found it easier to calibrate using the handheld interface. Using the handheld device was not without some effort, as it took some deciphering to translate the Torc's cryptic display. Once we recognized the display letters, we were able to successfully navigate the dial, and the tuning was quick and easy. Like the other systems, the Painless Torc offers two different shift calibrations. The difference is the Torc does not require a separate toggle switch, as switching can be quickly accomplished via the module. As with most of the controllers, it also incorporates Manutronic connections capable of driving paddle shifters such as the shifter offered by Twist Machine.

This was the last controller we tested, and we were successful in making the transmission shift the way we wanted. Even with our experience with the previous controllers, it took a little longer to tune the trans to our satisfaction. An item we thought could have been added was an rpm trigger directly from the distributor. Instead, the Torc chooses to simulate engine speed from the Transmission Input Speed Sensor (TISS), which is affected by torque converter slippage. Because of this, shift points are estimated based on vehicle speed. This is a minor point but important enough to warrant attention. Another feature worth mentioning is the system's five-year warranty, which illustrates Painless' confidence in this controller.

PCS Simple Shift ($599.00)

With a name like Simple Shift, you would expect it to be exactly that—simple to install and use. Once the harness is connected, all you have to do is set the dials on the side of the controller for the initial configuration as listed in the instruction manual, and you are ready for a testdrive. The initial setup is also the easiest, as you merely check TPS operation against the blinking light on the front of the controller. So right away, this controller was both affordable and easy to use, giving all appearances that it could be the most popular choice among car crafters. This was the third of the five controllers we tested, but we discovered we couldn't add more shift firmness beyond the most aggressive point. Jay Rohrback of Powertrain Control Systems (PCS) pointed out that we presented an interesting test by combining a very high- torque engine (more than 600 lb-ft) with a used transmission. Rohrback says PCS is considering offering a second controller for engines making more than 550 lb-ft of torque that would deliver additional trans pressure boost to hold that much torque. PCS sent one of these high-torque controllers to try, but it made only a minor improvement in shift firmness, and the trans still couldn't bark the tires during a WOT 1-2 shift at peak horsepower. This indicated to us that our trans was a little weak and could benefit from a shift improver kit. With a fresh trans, the shift firmness would have been more aggressive, with milder settings on the controller.

One cost of simplicity is a loss of finite control. For example, let's say you want the trans to shift at WOT at 6,200 rpm. Unfortunately, according to the instructions, the steps for WOT shift points 3 and 4 on the controller are either 6,075 or 6,425 rpm, respectively. There's no opportunity to set the shift point between these or any of the other steps. Each step at the higher engine speeds is about 6 percent, but in the lower engine speed it's closer to 9 percent. Just before we went to press, Rohrback informed us PCS will release a laptop-compatible program for the Simple Shift that will offer far more finite control and opportunities for tuning many of the shift parameters if that's something customers desire. So there you go.

TCI EZ-TCU ($614.95)

The TCI EZ-TCU is the only unit in our test fleet offering nearly complete hands-off tuning. The system uses self-learning software originally developed by its sister company, FAST, for the EZ-EFI system. The handheld unit will guide you through the initial setup once you have the system wired with a functioning TPS. The only inputs needed are the type of trans, rear tire diameter, rear gear ratio, speedometer output (which is only necessary if you are employing an electric speedometer), max shift rpm, and a very simple TPS calibration. With those completed, you can drive the car, and the EZ-TCU does the rest. Of course, if you want to go further into the setup, the handheld controller allows you to modify shift aggressiveness, shift firmness, and minimum speed for torque-converter clutch lockup. The handheld unit will also display lots of useful information such as rpm, mph, gear selected, trans oil temperature, battery voltage, and TPS percentage. If you're looking for a unit that requires the least amount of input that will get you driving with the least amount of fuss, this may be it. It's also important to note that if you are considering the TCI six-speed automatic that is based on the 4L80E, the EZ-TCU is the only controller we are aware of that will control this transmission. Overall, the system worked as advertised right out of the box. We modified the shift points slightly and adjusted when the lockup converter engaged, but other than a couple more mild changes including the maximum engine speed for shifts, the EZ-TCU performed flawlessly. Considering its affordability, it's tough to argue with this if all you want to do is plug in and drive.

Connections

The wiring harnesses on all the controllers look like a bed of snakes due to all the options that must be accommodated. But if all you are looking for is a basic system, making the connections to make the trans work is pretty simple. There are only three connectors that need to be attached to the transmission: the main harness connector, a transmission input shaft sensor (TISS), and the transmission output sensor (TOSS). The Painless Torc abbreviates that even further by only using the TISS connection. The remaining connections generally involve a constant 12-volt source, a switched 12-volt source, a good ground tied directly to the battery, and an rpm signal. The Torc system is simpler, as it does not require the rpm trigger or the constant 12-volt source. During our testing, we set the car up for quick-change electrical connections and had each box running in less than half an hour. Of course, we cheated and didn't mount any of the boxes in the car. It appears the hardest part of the entire installation would be routing the wires and mounting the box in a professional manner.

Application Chart

Controller

GM Transmissions

Ford Transmissions

4L60E/4L65E

AODE/4R70W

4L80E/4L85E

E4OD/4R100

HGM CompuShift II

YES

YES

GM CMPP Supermatic

YES

NO

Painless Torc

YES

YES

PCS Simple Shift

YES

YES

TCI EZ-TCU

YES

YES

The following is a list of the popular electronic overdrive transmissions.
Not all of these controllers will work with these transmissions.